JP3055378B2 - Control device for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an internal combustion engine in which lean combustion is performed under predetermined operating conditions, and more particularly to a control device for giving a correction at a high altitude.

[0002]

2. Description of the Related Art Conventionally, in order to mainly improve the fuel consumption rate, an internal combustion engine having an air-fuel ratio (A / F) of about 20 to 22 under a predetermined operating condition for performing lean combustion. Engine control devices are known. For example, Japanese Patent Laid-Open No. 2-7
Japanese Patent No. 0959 discloses that a swirl control valve provides a strong swirl in a cylinder to stabilize lean combustion, and an air-fuel ratio sensor provided in an exhaust system detects an actual air-fuel ratio along a target lean air-fuel ratio. Is shown in a closed loop control.

[0003]

In order to stably perform the above-described lean combustion, various elements such as a swirl ratio and an ignition timing must be properly controlled.
At a high altitude where the atmospheric pressure is low, the in-cylinder pressure is reduced due to the decrease in the atmospheric pressure, so that the atomization of the fuel supplied from the injector deteriorates, and as a result, the lean combustion becomes unstable.

When the air-fuel ratio is simply corrected so as to approach the stoichiometric air-fuel ratio at high altitude, knocking easily occurs.

[0005]

As shown in FIG. 1, a control device for an internal combustion engine according to the present invention includes an operating condition detecting means 1 for detecting an operating condition of an internal combustion engine and a lean air condition under a predetermined operating condition. Target air-fuel ratio setting means 2 for setting a target air-fuel ratio according to the detected operating conditions so as to obtain a fuel ratio, atmospheric pressure detecting means 3 for detecting atmospheric pressure, and an atmospheric pressure corresponding to the detected atmospheric pressure. A limit air-fuel ratio setting means 4 for setting a lean side air-fuel ratio so that the air-fuel ratio becomes smaller as the air-fuel ratio becomes lower, and a limit air-fuel ratio when the target air-fuel ratio corresponding to the operating condition is leaner than this limit air-fuel ratio. a given as the target air-fuel ratio the
The air-fuel ratio correction means 5 for correcting the target air-fuel ratio to a relatively rich side , and the correction amount is adjusted according to the correction amount of the target air-fuel ratio.
Ignition timing correction means 6 for correcting the ignition timing such that the ignition timing is adjusted to be more retarded .

[0006]

Under the operating conditions such as the steady running range, the target air-fuel ratio is set to the lean side and lean combustion is performed, but the limit air-fuel ratio setting means 4 detects the atmospheric pressure detected by the atmospheric pressure detecting means 3. , The lean air-fuel ratio is set such that the lower the atmospheric pressure, the closer to the stoichiometric air-fuel ratio. And
When the target air-fuel ratio corresponding to the operating condition is leaner than the limit air-fuel ratio, the target air-fuel ratio is corrected by the air-fuel ratio corrector 5 along the limit air-fuel ratio. That is, the target air-fuel ratio is limited so as not to be leaner than the limit air-fuel ratio. Accordingly, at high altitudes, leaning of the air-fuel ratio is suppressed in accordance with a decrease in atmospheric pressure so that stable combustion is maintained. When the air-fuel ratio is corrected in accordance with the atmospheric pressure as described above,
The ignition timing is corrected to the retard side by the ignition timing correction means 6 according to the correction amount. Thereby, the occurrence of knocking is suppressed.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below in detail with reference to the drawings.

FIG. 2 is a structural explanatory view showing a mechanical structure of the control device according to the present invention.
Denotes an intake passage, and 13 denotes an exhaust passage. The intake passage 12 is provided with an electromagnetic fuel injection valve 14 for supplying fuel toward each intake port, and a throttle valve 15 interposed therebetween. This throttle valve 15
Is detected by a throttle opening sensor 16 composed of a potentiometer. On the upstream side of the throttle valve 15, for example, a hot-wire type air flow meter 17 for detecting an intake air amount is provided. A swirl control valve 18, which is a butterfly valve having a cutout in a part of the valve body, is provided near the intake port of the intake passage 12. This swirl control valve 18 is
By closing the inflow direction of the intake when closing,
A strong swirl is generated in the cylinder, and is driven to be opened and closed by a diaphragm type negative pressure actuator 19. This negative pressure actuator 19 uses a negative pressure on the downstream side of the throttle valve 15 in the intake passage 12 as an operation source,
In addition, it is controlled on and off via a three-way electromagnetic system 20.

In the exhaust passage 13, for example, a catalytic converter 21 using a three-way catalyst is interposed, and an air-fuel ratio sensor 22 is disposed upstream of the catalytic converter 21. The air-fuel ratio sensor 22 is composed of a wide-range air-fuel ratio sensor such as an oxygen pump type sensor, and is capable of obtaining an output corresponding to the value of the air-fuel ratio including a lean region.

Reference numeral 23 denotes a water temperature sensor for detecting the cooling water temperature of the internal combustion engine 11, and reference numeral 24 denotes a crank angle sensor for generating a pulse signal at every predetermined crank angle so as to detect the engine speed.

The control unit 25 to which the detection signals of the above-mentioned various sensors are input uses a so-called microcomputer system.
27, a RAM 28, an I / O port 29, and the like. The control unit 25 includes an intake air amount detected by the air flow meter 17 and an air-fuel ratio sensor 2.
In addition to controlling the injection amount and the injection timing of the fuel injection valve 14 based on the detection signal 2 and the like, the ignition timing of the ignition plug 30 and the like are comprehensively controlled. Further, in this embodiment, an atmospheric pressure sensor 31 is built in the control unit 25, and detects an actual atmospheric pressure at a place where the internal combustion engine 11 is operated.

The basic operation of the control device having the above configuration will be described. First, as the air-fuel ratio control, the target air-fuel ratio AFT is determined based on a predetermined map from the intake air amount and the engine speed.
Are sequentially set, and the fuel injection amount is controlled so as to be set accordingly. FIG. 4 is a characteristic diagram showing the characteristics of the target air-fuel ratio AFT, and as shown in FIG. Stipulated. Then, the injection pulse width applied to the fuel injection valve 14 is controlled according to the target air-fuel ratio AFT. Further, the air-fuel ratio sensor 22 detects the actual air-fuel ratio from the exhaust gas composition. By multiplying the basic injection pulse width by a feedback correction coefficient calculated based on this detection signal, the actual air-fuel ratio can be accurately determined. Target air-fuel ratio AF
It is kept at T. Note that the swirl control valve 18 is open when the stoichiometric air-fuel ratio is attained.
0, the swirl control valve 18 is closed, and a strong swirl is generated in the cylinder.

On the other hand, in a place where the atmospheric pressure is low, such as at high altitude, as described above, the atomization of the fuel is deteriorated. Therefore, the target air-fuel ratio AFT is determined by the lean limit air-fuel ratio AFL corresponding to the atmospheric pressure value. Limited, preventing further leaning.

The ignition timing is set such that the advance angle value ADV is sequentially set based on a predetermined map based on the intake air amount and the engine speed, but when the swirl control valve 18 is closed. When the engine is open, the required ignition timing is different due to the difference in the air-fuel ratio. Therefore, two types of maps are provided in advance, and the non-lean region where the swirl control valve 18 is opened is provided. , And the map is switched in each of the lean regions where the swirl control valve 18 is closed. When the lean air-fuel ratio is limited to the limit air-fuel ratio AFL at high altitudes or the like as described above, the actual required ignition timing deviates from the ignition timing set in this map. Thus, the ignition timing is corrected to the retard side. FIG. 7 shows the relationship between the air-fuel ratio and the required ignition timing under a certain operating condition. As shown in the figure, the leaner the required ignition timing is, the more the required ignition timing is closer to the stoichiometric air-fuel ratio. , Relatively on the lag side. Therefore, if the air-fuel ratio is corrected to be small at a high altitude or the like, knocking is likely to occur at a normal ignition timing at the time of lean combustion.

FIG. 3 is a flowchart showing a specific processing flow of the above-described correction control for the atmospheric pressure.
Hereinafter, this will be described. Note that the process in FIG. 3 is repeatedly executed at regular intervals, for example.

First, in step 1, a target air-fuel ratio AFT is set based on engine operating conditions, specifically, the engine speed and the intake air amount. This is shown in FIG.
Is retrieved from the characteristic map shown in FIG. Then, in step 2, it is determined from the value of the target air-fuel ratio AFT whether or not the engine is in a lean region. In the non-lean range, that is, the stoichiometric air-fuel ratio or the rich air-fuel ratio, the atmospheric pressure is not adversely affected, so that the atmospheric pressure correction is not performed.

If it is determined in step 2 that the region is the lean region, the process proceeds to step 3 where the value of the atmospheric pressure detected by the atmospheric pressure sensor 31 is read. Then, in step 4, based on the value of the atmospheric pressure, the limit air-fuel ratio AFL on the lean side is set. The limit air-fuel ratio AFL is given in advance in the form of a table having characteristics as shown in FIG. 6 as a limit air-fuel ratio at which stable combustion can be maintained, and a value corresponding to the atmospheric pressure at that time is searched for. Is set by

Next, at step 5, the target air-fuel ratio AFT obtained from the operating conditions is compared with the limit air-fuel ratio AFL. If the target air-fuel ratio AFT is equal to or less than the limit air-fuel ratio AFL in step 5, stable lean combustion can be performed as it is, so that the correction after step 6 is not performed. In this case, the air-fuel ratio is controlled according to the target air-fuel ratio AFT, and the ignition timing is controlled by the advance value obtained from the lean ignition timing map. In step 5, if the target air-fuel ratio AFT is larger than the limit air-fuel ratio AFL,
Since the combustion deteriorates due to the decrease in the atmospheric pressure, step 6
Proceed to the subsequent steps to perform the correction. In step 6, the target air-fuel ratio AFT and the limit air-fuel ratio AFL are set as the air-fuel ratio correction amount ΔAF.
(AFT-AFL) is calculated. In step 7, an ignition timing correction amount ΔADV corresponding to the air-fuel ratio correction amount ΔAF is obtained. Specifically, the air-fuel ratio correction amount Δ
AF and the target air-fuel ratio AF at that time obtained from the operating conditions
Based on T, it is determined from a characteristic map as shown in FIG. The ignition timing correction amount ΔADV is given as a correction amount to the retard side, and the larger the value, the more the ignition timing is delayed. That is, as shown in FIG. 7, even if the air-fuel ratio correction amount ΔAF is the same, if the base air-fuel ratio is different, the required ignition timing changes differently. Map characteristics are set.

After the ignition timing correction amount ΔADV is thus determined, the target air-fuel ratio AFT is corrected in step 8 and the ignition timing is corrected in step 9. That is, in step 8, the target air-fuel ratio ΔAFT
As the limit air-fuel ratio A instead of the value obtained from the operating conditions.
The value of FL is given. As a result, as illustrated in FIG. 5, the target air-fuel ratio AFT is limited to the limit air-fuel ratio AFL, and the air-fuel ratio is kept at the limit which is the leanest within a range where deterioration of combustion does not occur. In step 9, the ignition timing is corrected to the retard side by subtracting the ignition timing correction amount ΔADV from the advance value searched based on the predetermined map. FIG. 5 shows that the engine speed is set to a constant value N1.
The relationship between the load and the air-fuel ratio when (see FIG. 4) is shown.

Therefore, according to the above-described embodiment, in a place where the atmospheric pressure is reduced, such as at a high altitude, the air-fuel ratio is always kept below the limit air-fuel ratio AFL. Be avoided. Then, as is apparent from FIG. 5, in a region where the target air-fuel ratio AFT obtained from the operating conditions is equal to or lower than the limit air-fuel ratio AFL, the correction based on the atmospheric pressure is not performed, so that a sufficiently lean air-fuel ratio can be maintained, and the combustion The fuel consumption rate can be maximized while avoiding deterioration of the fuel consumption. In addition, when the air-fuel ratio is corrected, the ignition timing is simultaneously corrected to the retard side, so that knocking can be reliably prevented.

[0021]

As is apparent from the above description, according to the control apparatus for an internal combustion engine according to the present invention, when the atmospheric pressure decreases at a high altitude or the like, the excessive leaning of the air-fuel ratio is suppressed,
Deterioration of combustion is reliably avoided. In particular, the correction is performed only when the target air-fuel ratio exceeds the limit air-fuel ratio, and in a region where the target air-fuel ratio obtained from the operating conditions is equal to or less than the limit air-fuel ratio,
Since the correction based on the atmospheric pressure is not performed, the leanest air-fuel ratio can be maintained within a range in which stable combustion can be performed, and the fuel consumption rate can be maximized while avoiding deterioration of combustion. In addition, when the air-fuel ratio is corrected, the ignition timing is simultaneously corrected to the retard side, so that knocking can be reliably prevented.

[Brief description of the drawings]

FIG. 1 is a claim correspondence diagram showing a configuration of the present invention.

FIG. 2 is a configuration explanatory view showing one embodiment of a control device according to the present invention.

FIG. 3 is a flowchart showing the flow of atmospheric pressure correction according to the embodiment.

FIG. 4 is a characteristic diagram showing characteristics of a target air-fuel ratio with respect to operating conditions.

FIG. 5 is a characteristic diagram showing characteristics of an air-fuel ratio at a constant rotation speed.

FIG. 6 is a characteristic diagram showing a characteristic of a limit air-fuel ratio with respect to an atmospheric pressure.

FIG. 7 is a characteristic diagram showing a relationship between an air-fuel ratio and a required ignition timing.

FIG. 8 is a characteristic diagram showing characteristics of an ignition timing correction amount.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Operation condition detection means 2 ... Target air-fuel ratio setting means 23 3-Atmospheric pressure detection means 34 4-Limit air-fuel ratio setting means 5 ... Air-fuel ratio correction means 6 ... Ignition timing correction means

Continuation of the front page (56) References JP-A-63-55339 (JP, A) JP-A-60-27748 (JP, A) JP-A-63-170537 (JP, A) JP-A-57-44767 (JP) (A) JP-A 1-222428 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) F02D 41/00-41/40 F02P 5/15 F02D 43/00

Claims (1)

(57) [Claims] An operating condition detecting means for detecting an operating condition of an internal combustion engine, and a target air-fuel ratio setting for setting a target air-fuel ratio in accordance with the detected operating condition so that a lean air-fuel ratio is obtained under a predetermined operating condition. Means, an atmospheric pressure detecting means for detecting the atmospheric pressure, and the lower the atmospheric pressure, the smaller the air-fuel ratio according to the detected atmospheric pressure.
A limit air-fuel ratio setting means for setting a limit air-fuel ratio on the lean side so that, when the target air-fuel ratio corresponding to operating conditions is leaner than this limit air-fuel ratio, giving the limit air-fuel ratio as the target air-fuel ratio Air-fuel ratio correction means for correcting the target air-fuel ratio to a relatively rich side , and in accordance with the correction amount of the target air-fuel ratio,
A control device for an internal combustion engine, comprising: ignition timing correction means for correcting the ignition timing to be on the retard side .